The present invention relates to an afterglow lamp, the inner surface of which is coated with a boroaluminate long decay phosphor of a specified composition having afterglow characteristics.
An enforcement ordinance of the Fire Service Act, the Fire Prevention Regulations of each city or the like obliges people to provide guide lamps in places where many people gather, such as theaters and hotels. When usual electric sources are cut on account of an earthquake, a fire or other disasters, it is necessary that reserve electric sources are automatically put on to light such guide lamps for more than 20 minutes. However, if the reserve electric sources are also cut or feeding circuits are cut on account of the disaster, the guide lamps are cut off. In such cases, a complicated underground market, a long tunnel, a multistory building at night and the like become very dangerous places. Further, since the conventional guide lamps are of complicated structure, it takes much time and high cost to provide the same. Therefore, such guide lamps are rarely provided except the places where the Laws oblige to equip the same.
Further, guide lamps are required not only in an emerbency such as mentioned above. If almost all buildings, including large buildings such as company buildings, department stores, school houses and factories, and stores and houses, are equipped with guide lamps of simple structure and low cost which allow the users to see their feet from the time when they turn off the switches of the lights of a room, corridor or staircase, until they reach the exit, they will be more safe and comfortable.
In this connection, providing a light storing substance capable of absorbing and storing optical energy emitted from a light source on a supporting member, such as a shade positioned in a place where the light from the light source reaches has been disclosed in Japanese Non-examined Patent Publication No.58-121088 issued Jul. 19,1983. By using this light storing substance, it becomes unnecessary to provide reserve electric sources. However, the conventional light storing substances are disadvantageous in that they are chemically unstable and are apt to be deteriorated by ultraviolet rays, high temperatures, moisture or the like. Further, the afterglow of these light storing substances is dark and short. Furthermore, sufficient light cannot be obtained by the method of coating a supporting member with a light storing substance.